firmware: arm_scmi: Add SCMI v3.1 powercap fast channels support

Add SCMIv3.1 powercap protocol fast channel support using common helpers
provided by the SCMI core with scmi_proto_helpers_ops operations.

Link: https://lore.kernel.org/r/20220704102241.2988447-5-cristian.marussi@arm.com


Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>